Ampelodesmos Link
Habit, vegetative morphology. Robust perennial; rhizomatous. Culms 60–350 cm high; herbaceous. Culm internodes solid. Leaves non-auriculate. Leaf blades harsh; narrow; flat, or rolled; not pseudopetiolate; without cross venation; a fringed membrane; not truncate; 6–12 mm long.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; open; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 10–15 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairy (villous). Hairy callus present.
Glumes two; more or less equal; shorter than the spikelets; shorter than the adjacent lemmas; pointed (acuminate); awnless; carinate; similar (firmly membranous). Lower glume 3–5 nerved. Upper glume 3–5 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets distal to the female-fertile florets. Spikelets without proximal incomplete florets.
Female-fertile florets 2–6 (?). Lemmas decidedly firmer than the glumes (leathery); not becoming indurated; incised; 2 lobed; not deeply cleft (shortly bidentate); mucronate, or awned. Awns when present, 1; from a sinus, or apical; non-geniculate; much shorter than the body of the lemma. Lemmas hairy (on the lower half); carinate to non-carinate; 5–7 nerved. Palea present; relatively long; apically notched (bidentate); awnless, without apical setae; 2-nerved; 2-keeled. Lodicules present; 3; free; membranous; ciliate (on the margins); not toothed; not or scarcely vascularized. Stamens 3. Anthers not penicillate. Ovary hairy. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit medium sized (about 7 mm long); with hairs confined to a terminal tuft. Hilum long-linear. Embryo small. Endosperm hard. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.
Seedling with a tight coleoptile. First seedling leaf with a well-developed lamina. The lamina narrow (l/b ratio 70); curved; 7 veined.
Abaxial leaf blade epidermis. Costal/intercostal zonation lacking. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs absent. Stomata absent or very rare; 28.5–30 microns long. Intercostal short-cells common; in cork/silica-cell pairs. Intercostal silica bodies elliptic. Costal short-cells predominantly paired. Costal silica bodies rounded (mostly, elliptical), or tall-and-narrow.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs (flat-topped ribs); with the ribs very irregular in sizes. Midrib not readily distinguishable; with one bundle only. Bulliforms not present in discrete, regular adaxial groups; in the furrows, in ill-defined groups of irregularly sized cells cf. Ammophila. All the vascular bundles accompanied by sclerenchyma. Sclerenchyma not all bundle-associated. The ‘extra’ sclerenchyma in a continuous abaxial layer.
Cytology. Chromosome base number, x = 12 (chromosomes small). 2n = 48 and 96. 4 and 8 ploid.
Taxonomy. Stipoideae; Ampelodesmeae.
Distribution, ecology, phytogeography. 1 species; Mediterranean. Xerophytic (mainly coastal).
Holarctic. Boreal and Tethyan. Euro-Siberian. Mediterranean. European.
Economic importance. A component of Esparto grass, used for papermaking.
References, etc. Morphological/taxonomic: Decker 1964b; Macfarlane and Watson 1980. Leaf anatomical: Metcalfe 1960; this project.
Special comments. An isolated monotypic genus, of uncertain taxonomic affinities in spite of the good descriptive data. A prime candidate for comparative DNA studies.
Illustrations. • Abaxial epidermis of leaf blade. Ampelodesmos mauritanicus. • Transverse section of leaf blade. Ampelodesmos mauritanicus.
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘Grass Genera of the World: Descriptions, Illustrations, Identification, and Information Retrieval; including Synonyms, Morphology, Anatomy, Physiology, Phytochemistry, Cytology, Classification, Pathogens, World and Local Distribution, and References.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).
